This invention relates to a mixture compressing internal-combustion engine and, in particular, to an engine wherein the maximum throttle opening is controlled as a function of signals emitted by a knocking sensor.
Conventional anti-knocking devices operate by retarding the moment of ignition whenever a knock sensor signals the occurrence of knocking phenomena. However, such change in the moment of ignition results in a loss of power as well as higher specific fuel consumption.
Copending patent application Ser. No. 219,352 filed Dec. 22, 1980, now U.S. Pat. No. 4,364,353, by Ernst Fiala and assigned to the present assignee, discloses an anti-knocking device in which, when knocking occurs, the firing angle is shifted until a limit value is reached. Thereafter, if knocking has not stopped, the throttle valve serving as the air control member is adjusted to provide a smaller throttle opening. However, this results in some increase in specific fuel consumption during knocking.
German Offenlegungschrift No. 2,551,912 discloses the provision of a deformable hollow bellows in the connection between the gas or accelerator pedal and the throttle, the interior of the hollow bellows being in communication with the suction side of the engine suction line. The interposition of the bellow between the gas pedal and the throttle tends to prevent knocking, rather than eliminating knocking that has already occurred, by reducing the opening angle of the throttle under high load. This occurs because the length of the link between the throttle and gas pedal is increased when a signal indicating a low suction pipe vacuum has been received. A disadvantage to this system is that it is not a regulating process in which the throttle opening is reduced upon the occurrence of knocking until knocking disappears. Rather, the bellows and other retraction spring devices perform a one-time "calibration" of the throttle with respect to the respective fuel employed, and a permanent power loss must be accepted regardless of whether knocking is actually present.
An object of the present invention is to provide an anti-knocking device which acts as a regulator in that it permits driving at the knocking limit while avoiding permanent power loss. Further, if knocking does occur, the specific fuel consumption is not increased.